Adsorption, desorption and surface reactions of CO and NO on Pd{320}

Adsorption, desorption and a surface reaction between coadsorbed CO and NO on a stepped Pd{320} (Pd(S)[3(110) x (100)]) surface have been studied using molecular beam surface scattering (MBSS), temperature-programmed desorption/reaction (TPD/TPR) and X-ray photoelectron spectroscopy (XPS). CO adsorbs molecularly on Pd{320} with an initial sticking probability close to unity at 300 K, and reversibly desorbs upon heating according to the first-order desorption kinetics. NO adsorption on Pd{320} is molecular in the temperature range of 300-400 K as indicated by MESS and XPS. NO desorbs molecularly in addition to the formation of relatively large amounts of N-2 and N2O near 500 K. Coadsorbed NO and CO are observed to react upon heating to produce an extremely narrow TPR peak of CO2 at similar to 470 K. The location and half-width of the CO2 TPR peak are almost independent of the initial coverages of CO and NO, which indicates an autocatalytic behaviour of the NO-CO reaction kinetics on Pd{320}. (C) 1998 Elsevier Science B.V. All rights reserved.